1. Field of the Invention
The invention relates to the field of container closures and particularly of liquid and food container sealing. It addresses two processes to condition both the edge of the opening of the plastic or metal container and the extensible polymer film to be applied thereto with the process disclosed in Patent Application Ribi WO 98/32668 of Jan. 23, 1998.
Thanks to such conditioning, performed with various devices allowing to perform the processes, an effective and safe sealing effect is obtained.
2. Related Art
In prior art sealing techniques, liquid and/or food containers are typically sealed either by means of bonded screw plugs or metal plugs, or by the application of various metal disks, to be attached to the edge of the opening, or with blind seals, which are held in position by other mechanical devices, like those mentioned above.
A more practical, cost-effective, hence industrially advantageous arrangement is proposed by the invention disclosed in Patent Application WO 98/32688 of Jan. 23, 1998, and various implementations thereof, i.e. devices for applying extensible polymer films to the edges of the openings of glass containers.
Nevertheless, this arrangement cannot be used for plastic or metal containers because, as explained below, adhesion thereof is hindered by the electrostatic charges of equal polarity on the faces of the two materials to be attached or simply due to the lack of electric charges on said faces.